In systems for circulating hot or cold fluids to disposable devices, as for example thermal pads for application to the human body, a flexible tube attached to the pad is coupled to a poppet valve or the like on the circulating equipment. The pad and the attached flexible tube are normally disposable items, so that when the coupling device is unscrewed from the valve it must be detached from the disposable tube for reuse. The operation of connecting and disconnecting the tube to and from the coupling device together with disconnecting the coupling device from the valve takes excessive time, and, moreover, the user is apt to carelessly throw away the relatively expensive coupling device along with the disposable tube and pad.